William J. Brennan, Jr.

“ Similarly here, a conclusive presumption that a recently established resident is not a resident at all for voting purposes is simply an overbroad burden upon the right to vote. In most cases, it is no more difficult to determine whether one recently arrived in the community has sufficient intent to remain to qualify as a resident than it is to make a similar determination for an older inhabitant. ”

“ The appellees argue that the State's durational residency requirement is necessary to ensure the purity of its elections. The impurities feared ('dual voting' and 'colonization') all involve the same evil-voting by nonresidents, either singly or in blocks. But it is difficult to see how the durational residency requirement in any way protects against nonresident voting. The qualifications of the would-be voter in Colorado are determined when he registers to vote, which he may do until 20 days before the election. ”

“ But if it was not clear in 1965 it is clear now that once a State has determined that a decision is to be made by popular vote, it may exclude persons from the franchise only upon a showing of a compelling interest, and even then only when the exclusion is the least restrictive method of achieving the desired purpose. ”

“ This is because ordinarily a person's standing to make that challenge would not mature unless he had become a Colorado resident within two months prior to a presidential election. Barring resort to extraordinary expedients, that interval is obviously too short for the exhaustion of state administrative remedies and the completion of a lawsuit through filing of the complaint in a federal district court, convening of a three-judge court, trial, and review by this Court. ”